1. Field of the Invention
The present invention relates generally to an electronic power steering system (EPS) for a vehicle and, more particularly, to an EPS motor having a steering angle sensor mounted to an electronic power steering system.
2. Description of the Related Art
Generally, an auxiliary steering system supported by additional power is used to ensure the steering stability of a vehicle. Conventionally, the auxiliary steering system uses a hydraulic pressure. However, recently, an electronic power steering system, which consumes less power and is excellent in accuracy, has been used.
Such an electronic power steering system (EPS) controls the driving of a motor by an electronic control unit (ECU) depending on driving conditions detected by a vehicle speed sensor, a torque angle sensor and a torque sensor, thus ensuring stability in cornering of a vehicle and providing a rapid restoring force, and thereby allowing a driver to safely drive the vehicle.
FIG. 1 is a schematic view showing the construction of a typical electronic power steering system.
As shown in the drawing, the electronic power steering system includes a steering wheel 10, a steering shaft 10a, an EPS motor 11, a steering angle sensor 12 and an ECU 13.
The steering wheel 10 is rotated by a driver so as to change a direction of a vehicle. The steering wheel 10 is connected to the steering shaft 10a. If the driver rotates the steering wheel 10, the steering shaft 10a rotates in the same direction as the steering wheel 10 in conjunction with the rotation of the steering wheel 10.
The EPS motor 11 is a motor that assists torque of the steering wheel 10 manipulated by a driver for steering, and enables the driver to more conveniently perform steering operation. Generally, the EPS motor 11 uses a brushless DC (BLDC) motor. The BLDC motor means a DC motor equipped with an electronic commutating device except for mechanical contact parts of the DC motor such as a brush or a commutator. A decelerator and a torque sensor (not shown) are coupled to an end of the EPS motor 11. The torque sensor detects relative rotating displacement between an input shaft and an output shaft when the steering wheel 10 rotates, generates an electric signal based on the detected result, and thereafter transmits the signal to the ECU 13.
The steering angle sensor 12 is installed at a position around the steering wheel 10, directly measures a rotating angle of the steering wheel 10 rotated by the driver's manipulation, and transmits a signal regarding the rotating angle to the ECU 13.
The ECU 13 electronically controls various drive sources of the electronic power steering system including the EPS motor 11, based on data of a vehicle speed sensor (not shown), the torque sensor and the steering angle sensor 12.
However, the electronic power steering system constructed as described above is problematic in that the steering angle sensor 12 is mounted as a separate part, so that an additional space for installing the steering angle sensor 12 must be provided around the steering wheel 10, thus causing inconvenience, and the number of assembling processes and the cost of parts are increased because of an increase in number of parts.